There should have been a 'slug' attached to the clew that slid into the groove on top of the boom.. that would have kept the clew from lifting off, then the outhaul applies the foot tension. If that's missing then a clew strap would be needed. Like so:

For a bit of extra power you could double your outhaul as shown in that picture too..

__________________
Ron

1984 Fast/Nicholson 345 "FastForward"

".. there is much you could do at sea with common sense.. and very little you could do without it.."
Capt G E Ericson (from "The Cruel Sea" by Nicholas Monsarrat)